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Ideal Logic fault F4

Flow thermistor fault

Gas boiler

What it means

Flow temperature sensor reading is out of range or disconnected

Likely causes

  1. Flow thermistor resistance out of specification
  2. Flow thermistor wiring disconnected
  3. Flow thermistor wiring lacks continuity to PCB
  4. PCB fault

Where to start

  1. Remove flow thermistor from CH flow pipe
  2. Disconnect thermistor wires
  3. Measure resistance across thermistor terminal pins using multimeter

The full answer, free

  • The readings and component tests from the manual
  • How to put it right, step by step
  • The manual page for this fault (page 49), right under the answer
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Safety: Isolate gas and power before you open the case. If you have been into the gas side, do a tightness test, and a combustion and flue check before you hand back. Gas Safe (UK) or RGI (Ireland) work only.

From the Ideal manual for the Logic. Check the model on the data plate before you order parts.

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